Organic-inorganic halide perovskite solar cells have rapidly come to prominence in the photovoltaic field. In this context, CH3 NH3 PbI3 , as the most widely adopted active layer, has been attracting great attention. Generally, in a CH3 NH3 PbI3 layer, unreacted PbI2 inevitably coexists with the perovskite crystals, especially following a two-step fabrication process. There appears to be a consensus that an appropriate amount of unreacted PbI2 is beneficial to the overall photovoltaic performance of a device, the only disadvantageous aspect of excess residual PbI2 being viewed as its insulating nature. However, the further development of such perovskite-based devices requires a deeper understanding of the role of residual PbI2 . In this work, PbI2 -enriched and PbI2 -controlled perovskite films, as two extreme cases, have been prepared by modulating the crystallinity of a pre-deposited PbI2 film. The effects of excess residual PbI2 have been elucidated on the basis of spectroscopic and optoelectronic studies. The initial charge separation, the trap-state density, and the trap-state distribution have all been found to be adversely affected in PbI2 -enriched devices, to the detriment of photovoltaic performance. This leads to a biphasic recombination process and accelerates the charge carrier recombination dynamics.

Behind the outstanding photovoltaic performance of perovskite solar cells (PSCs), the correlation between the structural configuration of the PSCs and the mechanism of photoelectric conversion is still not fully understood. In this paper, two types of PSCs with different structural configurations, that is, mesoporous (meso) and planar, were prepared, and systematic optoelectronic transient studies were performed on these devices. Although the photovoltaic performances of the tested meso-and planar-PSCs were comparable, the different structural configurations resulted in distinct charge dynamics and photoelectric conversion mechanisms. By taking the dynamic results into account, the influence of a meso-TiO2 layer on charge accumulation, transport, and recombination was elucidated. More importantly, an excessively slow temporal response component in the optoelectronic transients was observed, which was proven to be linked to specific hysteresis phenomena in the PSCs. The experimental results collectively indicated that the hysteresis, which showed strong dependence on device structure and charge dynamics, was irrelevant to charge trapping or ferroelectricity but probably resulted from interfacial charge accumulation and/or ion migration. This work provides deep insight into the structure-function relationship in PSCs and highlights the effect of hysteresis on charge dynamics.

Admixing PCBM and its dimer as electron transport material significantly improves charge carrier dynamic behavior in inverted perovskite device.

The photovoltaic performance of planar perovskite solar cell is significantly influenced by the morphology of perovskite film. In this work, five kinds of devices with different perovskite film morphologies were prepared by varying the concentration of CH3NH3Cl in precursor solutions. We found that best morphology of perovskite film results in the excellent photovoltaic performance with an average efficiency of 15.52% and a champion efficiency of 16.38%. Transient photovoltage and photocurrent measurements are performed to elucidate the mechanism of photoelectric conversion processes, which shows that the charge recombination is effectively suppressed and the charge transport is obviously promoted by optimized morphology. (C) 2016 Elsevier B.V. All rights reserved.

Organic-inorganic halide perovskite solar cells are becoming the next big thing in the photovoltaic field owing to their rapidly developing photoelectric conversion performance. Herein, mesoporous structured perovskite devices with various perovskite grain sizes are fabricated by a sequential dropping method, and the charge recombination dynamics is investigated by transient optical-electric measurements. All devices exhibit an overall power conversion efficiency around 15%. More importantly, a biphasic trap-limited charge recombination process is proposed and interpreted by taking into account the specific charge accumulation mechanism in perovskite solar cells. At low Fermi levels, photo-generated electrons predominately populate in the perovskite phase, while at high Fermi levels, most electrons occupy traps in mesoporous TiO2. As a result, the dynamics of charge recombination is, respectively, dominated by the perovskite phase and mesoporous TiO2 in these two cases. The present work would give a new perspective on the charge recombination process in meso-structured perovskite solar cells.

Fully indium-free flexible Ag nanowires/ZnO:F composite transparent conductive electrodes with high haze can improve the perovskite solar cell efficiency.

Material-abundant ZnO and metal thin film have been proposed as potential alternatives for the most widely commercial indium tin oxide (ITO) transparent and conductive electrode. Yet the deterioration of optical transparency and conductivity for these materials makes them difficult to compete with ITO. In this work, a double-layer structured film-composed of FZO and Cu film is presented at room temperature, which combines the high transparency of FZO and high conductivity of Cu film. We first studied the effect of oxygen pressure on the transparency and conductivity of free-standing FZO layer deposited on poly(ethylene terephthalate) (PET) by PLD method. Also the structural, electrical, and optical properties of bilayers electrode dependence on the Cu layer thickness were optimized in detail. As the Cu layer thickness increases, the resistivity decreases. The lowest resistivity of 6.6 x 10(-5) Omega cm with a carrier concentration of 1.11 x 10(22) cm(-3) and mobility of 8.52 cm(2) V-1 s(-1)was obtained at the optimum Cu( 12 nm) layer thickness. We find that FZO layer have anti-reflection effect for Cu/FZO (250 nm) bilayer in the wavelength range of 650-1000 nm compared with single Cu layer. And we firstly study the stretchable performance for Cu film-based composite electrodes with stretching ratio changing from 0 to 5%. Furthermore, we study excellent mechanical flexibility and stability of composite electrodes by bending test. (C) 2015 Elsevier B.V. All rights reserved.

Copper (I) iodide (CuI) films are grown on glass substrates with a direct vacuum thermal evaporation method, and the effect of substrate temperature on their photoluminescence and transparent conductive properties is discussed. The X-ray diffraction (XRD) measurement identifies the polycrystalline CuI film has gamma-phase with (111) preferential growth direction. When the substrate temperature is optimised at 120 degrees C, the average transmittance is about 90% in the wavelength range of 410-1500 nm. The electrical properties measured by Hall effect show the lowest resistivity of 1.0 X 10(-2) Omega cm with hole concentration of 3.0 X 10(19) cm(-3) and mobility of 25 cm(2)V(-1)s(-1). These results indicate that direct thermal deposition is a simple method to grow high quality p-type CuI films. (C) 2015 WILEY - VCH Verlag GmbH & Co. KGaA, Weinheim

Arrays of ZnO/CdS/CdSe core/shell nanocables with different annealing temperatures have been investigated for CdS/CdSe quantum dots sensitized solar cells (QDSSCs). CdS/CdSe quantum dots were synthesized on the surface of ZnO nanorods that serve as the scaffold via a simple ion-exchange approach. The uniform microstructure was verified by scanning electron microscope and transmission electron microscope. UV-Visible absorption spectrum and Raman spectroscopy analysis indicated noticeable influence of annealing temperature on the interface structural and optical properties of the CdS/CdSe layers. Particularly, the relationship between annealing temperatures and photovoltaic performance of the corresponding QDSSCs was investigated employing photovoltaic conversion, quantum efficiency and electrochemical impedance spectra. It is demonstrated that higher cell efficiency can be obtained by optimizing the annealing temperature through extending the photoresponse range and improving QD layer crystal quality.

The influences of aluminum doping, oxygen pressure, and substrate temperature on the transparent conductive properties of ZnO:Al (AZO) films grown by pulsed laser deposition (PLD) were investigated using scanning electron microscope, atomic force microscope, X-ray diffraction, Hall effect measurements, and optical transmission spectrum. When the aluminum doping concentration is over 0.5 wt%, all the PLD grown AZO films are degenerated and the aluminum donors are thermal ionized even at a low temperature of 80 K. As a result, the bandgap of AZO film shows blue shifts due to the Bernstein-Moss effect as further confirmed by optical transmission spectrum. The influences of the oxygen pressure and substrate temperature on the transparent conductive property of AZO films were further studied. When the oxygen pressure is 1 Pa and the substrate temperature is 200 ℃, the best conductivity property of AZO thin film is obtained with Hall mobility of 28.8 cm2/V·s and film resistivity of 2.7×10-4 Ω·cm. Moreover, the light transmittance in the visible range exceeds 85%. However, as the oxygen pressure and temperature continue to increase, the film resistivity will increase.

This paper proposes an optimal design method for passive filters based on an optimal tuned frequency,which can ensure the detuning filter still has the best efficiency.The optimization model based on the optimal tuned frequency selects the capacitance of each branch as an independent optimization variable and minimizes the total voltage harmonic distortion,considering the reactive power balance,the harmonic voltage and harmonic current limits.The optimal compensation capacity and the optimal tuned frequency can be obtained through the iterative algorithm.A study case shows that the filters designed with the proposed method has better efficiency as compared to those filters designed with experience.

The basic principle and structure of the 24-pulse rectifier are studied in this paper.Two methods for realizing the 24-pulse rectifier model in PSCAC/EMTDC are proposed,include three single phase auto-transformer method and three-winding transformer method.A test system is used to verify the validity of the model,and the simulation results show that the rectified waveform and the harmonic components are in consistent with the theoretical results.